Duchenne Muscular Dystrophy (DMD)

A genetic disease with a devastating impact

Duchenne muscular dystrophy (DMD) is a devastating diagnosis for a family to receive. It is one of the most common recessive genetic disorders, affecting around 1 in every 5,000 boys born each year around the world.

While DMD is rare, its impact is severe and life-altering for affected children and their families. Caused by a mutation in the dystrophin gene – which encodes for a critical protein that protects muscles from damage – DMD causes progressive muscle weakness throughout the body, that eventually impacts mobility, breathing and the heart. As the incurable disease progresses, it results in death, usually between 21 and 40 years of age.

With DMD, new activities are gained over time and then lost over time, and that’s the most heartbreaking thing.

Patricia Furlong
President and Founder of Parent Project Muscular Dystrophy

The slow erosion of strength

The early signs of DMD are typically first noticed between 16 months to 3 years of age. Muscles that should become stronger with age begin to fail, and those with DMD typically experience a range of symptoms including:

Developmental delay

Children with DMD often achieve milestones like standing, walking or talking later than their peers.

Progressive muscle weakness

Everyday activities like getting up, standing, jumping, or climbing the stairs require more effort, and children with DMD experience frequent falls until eventually they are no longer able to perform these activities at all.

Scoliosis and muscle contractures

Muscles become shorter and very tight, which can make it harder to move. As the back muscles weaken, abnormal spinal curvature can occur. This not only causes pain but can also worsen respiratory problems and impair mobility further.

Weakening of the heart and lungs

As DMD progresses, the muscles of the heart and lungs can become weaker, leading to life-threatening complications. Teens and young adults with DMD often require heart medications and ventilatory support to continue to breathe.

For boys living with DMD, even the simplest moments can become battles. Patricia Furlong is the President and Founder of Parent Project Muscular Dystrophy (PPMD), a patient advocacy organisation dedicated to supporting patients with DMD and their families. Listen as she describes her personal experience as the mother of children living with DMD.

Understanding the cause of DMD

DMD is an X-linked recessive condition that is passed down through families and primarily affects males. This is because the dystrophin gene that causes DMD is located on the X chromosome:

• As boys only inherit one X chromosome, if that contains the gene mutation for DMD, then the child will have the disease.
• As girls have two X chromosomes, as long as they inherit one normal copy of the dystrophin gene, they will usually experience either no symptoms or the symptoms will be mild. These girls are carriers of DMD and can pass the defective gene on to their children.

While DMD is primarily thought of as an inherited disease, it is important to note that around 30% of DMD cases are due to spontaneous mutations in the dystrophin gene and affect families with no prior history of the disease.

The diagnosis of DMD typically involves a combination of family history, clinical observations, blood tests, genetic testing, and in some instances, muscle biopsy.

From onset to progression

DMD is a progressive disease that follows a distinct and devastating trajectory:

The typical life expectancy of DMD is between 21–40 years. Although there is currently no cure, treatment advances may allow children who are diagnosed today to live into their fourth decade.

Behind the diagnosis: The psychosocial impact of DMD

DMD doesn’t just affect patients physically; it is a life-altering diagnosis that takes a profound emotional and psychological toll on patients and their families. DMD comes with significant neurological and cognitive implications which are likely due to dystrophin deficiency in the brain:

• 24–29% experience anxiety
• 17–27% experience depression
• 3–20% have autism spectrum disorder
• 11–32% have attention deficit/hyperactivity disorder (ADHD)
• 5–11% have obsessive–compulsive disorder (OCD)

Caring for a child with DMD is also a full-time job, that is both emotionally demanding and often financially damaging:

• ~ 50% of caregivers experience moderate or severe levels of anxiety or depression.
• Up to 49% of caregivers reduce their working hours or stop working completely because of their child’s DMD.
• Sleep deprivation, impaired health and reduced work life productivity are common.

Listen to Patricia Furlong, President and Founder of PPMD, discuss the tremendous impact DMD has on patients and their entire families.

DMD by the numbers

1 in every 5,000 boys born each year globally are affected by DMD. ~30% of DMD cases are due to spontaneous mutations and affect families with no known family history. 12years: By that age, most children have lost their ability to walk. 100%: with no cure, DMD is fatal in all cases.

Addressing a key unmet need for patients and their families

For families facing a DMD diagnosis, treatment options today are not curative and cannot prevent disease progression. Corticosteroids are the current standard of care, which can help slow the progression of muscle deterioration, giving children more years of mobility and independence. However, they come with significant side effects including:

Weight gain

Behavioural changes

Delayed puberty

Increased risk of fractures

Cushingoid appearance

Stunted growth

Over time, the cumulative impact of these side effects can be significant. Families need to find a balance between preserving function and managing detrimental side effects, all while watching their child’s condition worsen. As a result, there is an urgent need for safer and more effective treatment options.

At Grünenthal, we are working to improve the lives of those living with DMD—by developing a new treatment option with the potential for better efficacy than the current standard-of-care, with a lower side effect burden for patients.